This invention relates to shielded cells having manipulators comprising a master arm and a slave arm with a linking part between the arms.
Such cells are frequently used for handling alpha-emitting materials such as plutonium. As alpha contamination risks can arise from airborne substances any shielded cell therefore is expected to have a high standard of containment of such airborne substances at all times. In the past, alpha-emitting materials have been handled in a compartment (sometimes called a "glove box").
The master-slave manipulator is sealed in the glove box and the slave arm is encased in a sealing gaiter which extends from the shoulder to the wrist. For removal of the slave arm for servicing or replacement a complicated procedure of introducing the slave arm into protective bags is adopted and, whilst this is intended to maintain a high standard of containment, possibilities arise that slight airborne contamination can reach operator occupied regions. For current limitations on alpha contamination this known procedure is quite adequate but for a much reduced limit on alpha contamination (eg 1% of the currently accepted maximum permissible limit) improved methods of removing slave arms are required. The present invention provides such improved methods.